'well-worded' originates from Modern English as a compound of the adverb 'well' and the past-participial adjective 'worded' (from 'word' + '-ed').

'well' comes from Old English 'wel' meaning 'in a good manner', and 'worded' derives from Old English 'word' (word) with the past-participle/adjectival suffix '-ed'; the two elements were combined in Modern English into the compound adjective 'well-worded'.

Initially each element meant 'in a good manner' ('well') and 'expressed in words' ('worded'); over time the compound came to be used specifically to describe phrasing that is particularly apt or effective.